Fix bug in handling of quoted linker script tokens and update tests to use it.

There was an off by one error because the StringRef.substr functions
second argument is a length, not the end index.

Also updated a few ELF files which failed when run on Jenkins with paths
including the @ character.  This is often used in Jenkins for shared
workspace plugin.

Reviewed by Rui Ueyama

llvm-svn: 258583